summaryrefslogtreecommitdiff
path: root/modules/caddyhttp/templates/templates.go
blob: 8f2ae9dcfc373287997c43364f7552bb2eb0324e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package templates

import (
	"bytes"
	"errors"
	"fmt"
	"net/http"
	"strconv"
	"strings"

	"github.com/caddyserver/caddy/v2"
	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
)

func init() {
	caddy.RegisterModule(Templates{})
}

// Templates is a middleware which executes response bodies as Go templates.
// The syntax is documented in the Go standard library's
// [text/template package](https://golang.org/pkg/text/template/).
//
// ⚠️ Template functions/actions are still experimental, so they are subject to change.
//
// [All Sprig functions](https://masterminds.github.io/sprig/) are supported.
//
// In addition to the standard functions and the Sprig library, Caddy adds
// extra functions and data that are available to a template:
//
// ##### `.Args`
//
// A slice of arguments passed to this page/context, for example as the result of a `include`.
//
// ```
// {{index .Args 0}} // first argument
// ```
//
// ##### `.Cookie`
//
// Gets the value of a cookie by name.
//
// ```
// {{.Cookie "cookiename"}}
// ```
//
// ##### `env`
//
// Gets an environment variable.
//
// ```
// {{env "VAR_NAME"}}
// ```
//
// ##### `placeholder`
//
// Gets an [placeholder variable](/docs/conventions#placeholders).
// The braces (`{}`) have to be omitted.
//
// ```
// {{placeholder "http.request.uri.path"}}
// {{placeholder "http.error.status_code"}}
// ```
//
// ##### `.Host`
//
// Returns the hostname portion (no port) of the Host header of the HTTP request.
//
// ```
// {{.Host}}
// ```
//
// ##### `httpInclude`
//
// Includes the contents of another file by making a virtual HTTP request (also known as a sub-request). The URI path must exist on the same virtual server because the request does not use sockets; instead, the request is crafted in memory and the handler is invoked directly for increased efficiency.
//
// ```
// {{httpInclude "/foo/bar?q=val"}}
// ```
//
// ##### `import`
//
// Imports the contents of another file and adds any template definitions to the template stack. If there are no defitions, the filepath will be the defition name. Any {{ define }} blocks will be accessible by {{ template }} or {{ block }}. Imports must happen before the template or block action is called
//
// **filename.html**
// ```
// {{ define "main" }}
// content
// {{ end }}
// ```
//
// **index.html**
// ```
// {{ import "/path/to/file.html" }}
// {{ template "main" }}
// ```
//
// ##### `include`
//
// Includes the contents of another file and renders in-place. Optionally can pass key-value pairs as arguments to be accessed by the included file.
//
// ```
// {{include "path/to/file.html"}}  // no arguments
// {{include "path/to/file.html" "arg1" 2 "value 3"}}  // with arguments
// ```
//
// ##### `listFiles`
//
// Returns a list of the files in the given directory, which is relative to the template context's file root.
//
// ```
// {{listFiles "/mydir"}}
// ```
//
// ##### `markdown`
//
// Renders the given Markdown text as HTML. This uses the
// [Goldmark](https://github.com/yuin/goldmark) library,
// which is CommonMark compliant. It also has these plugins
// enabled: Github Flavored Markdown, Footnote and syntax
// highlighting provided by [Chroma](https://github.com/alecthomas/chroma).
//
// ```
// {{markdown "My _markdown_ text"}}
// ```
//
// ##### `.RemoteIP`
//
// Returns the client's IP address.
//
// ```
// {{.RemoteIP}}
// ```
//
// ##### `.Req`
//
// Accesses the current HTTP request, which has various fields, including:
//
//    - `.Method` - the method
//    - `.URL` - the URL, which in turn has component fields (Scheme, Host, Path, etc.)
//    - `.Header` - the header fields
//    - `.Host` - the Host or :authority header of the request
//
// ```
// {{.Req.Header.Get "User-Agent"}}
// ```
//
// ##### `.OriginalReq`
//
// Like .Req, except it accesses the original HTTP request before rewrites or other internal modifications.
//
// ##### `.RespHeader.Add`
//
// Adds a header field to the HTTP response.
//
// ```
// {{.RespHeader.Add "Field-Name" "val"}}
// ```
//
// ##### `.RespHeader.Del`
//
// Deletes a header field on the HTTP response.
//
// ```
// {{.RespHeader.Del "Field-Name"}}
// ```
//
// ##### `.RespHeader.Set`
//
// Sets a header field on the HTTP response, replacing any existing value.
//
// ```
// {{.RespHeader.Set "Field-Name" "val"}}
// ```
//
// ##### `splitFrontMatter`
//
// Splits front matter out from the body. Front matter is metadata that appears at the very beginning of a file or string. Front matter can be in YAML, TOML, or JSON formats:
//
// **TOML** front matter starts and ends with `+++`:
//
// ```
// +++
// template = "blog"
// title = "Blog Homepage"
// sitename = "A Caddy site"
// +++
// ```
//
// **YAML** is surrounded by `---`:
//
// ```
// ---
// template: blog
// title: Blog Homepage
// sitename: A Caddy site
// ---
// ```
//
//
// **JSON** is simply `{` and `}`:
//
// ```
// {
// 	"template": "blog",
// 	"title": "Blog Homepage",
// 	"sitename": "A Caddy site"
// }
// ```
//
// The resulting front matter will be made available like so:
//
// - `.Meta` to access the metadata fields, for example: `{{$parsed.Meta.title}}`
// - `.Body` to access the body after the front matter, for example: `{{markdown $parsed.Body}}`
//
//
// ##### `stripHTML`
//
// Removes HTML from a string.
//
// ```
// {{stripHTML "Shows <b>only</b> text content"}}
// ```
//
type Templates struct {
	// The root path from which to load files. Required if template functions
	// accessing the file system are used (such as include). Default is
	// `{http.vars.root}` if set, or current working directory otherwise.
	FileRoot string `json:"file_root,omitempty"`

	// The MIME types for which to render templates. It is important to use
	// this if the route matchers do not exclude images or other binary files.
	// Default is text/plain, text/markdown, and text/html.
	MIMETypes []string `json:"mime_types,omitempty"`

	// The template action delimiters. If set, must be precisely two elements:
	// the opening and closing delimiters. Default: `["{{", "}}"]`
	Delimiters []string `json:"delimiters,omitempty"`
}

// CaddyModule returns the Caddy module information.
func (Templates) CaddyModule() caddy.ModuleInfo {
	return caddy.ModuleInfo{
		ID:  "http.handlers.templates",
		New: func() caddy.Module { return new(Templates) },
	}
}

// Provision provisions t.
func (t *Templates) Provision(ctx caddy.Context) error {
	if t.MIMETypes == nil {
		t.MIMETypes = defaultMIMETypes
	}
	if t.FileRoot == "" {
		t.FileRoot = "{http.vars.root}"
	}
	return nil
}

// Validate ensures t has a valid configuration.
func (t *Templates) Validate() error {
	if len(t.Delimiters) != 0 && len(t.Delimiters) != 2 {
		return fmt.Errorf("delimiters must consist of exactly two elements: opening and closing")
	}
	return nil
}

func (t *Templates) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
	buf := bufPool.Get().(*bytes.Buffer)
	buf.Reset()
	defer bufPool.Put(buf)

	// shouldBuf determines whether to execute templates on this response,
	// since generally we will not want to execute for images or CSS, etc.
	shouldBuf := func(status int, header http.Header) bool {
		ct := header.Get("Content-Type")
		for _, mt := range t.MIMETypes {
			if strings.Contains(ct, mt) {
				return true
			}
		}
		return false
	}

	rec := caddyhttp.NewResponseRecorder(w, buf, shouldBuf)

	err := next.ServeHTTP(rec, r)
	if err != nil {
		return err
	}
	if !rec.Buffered() {
		return nil
	}

	err = t.executeTemplate(rec, r)
	if err != nil {
		return err
	}

	rec.Header().Set("Content-Length", strconv.Itoa(buf.Len()))
	rec.Header().Del("Accept-Ranges") // we don't know ranges for dynamically-created content
	rec.Header().Del("Last-Modified") // useless for dynamic content since it's always changing

	// we don't know a way to quickly generate etag for dynamic content,
	// and weak etags still cause browsers to rely on it even after a
	// refresh, so disable them until we find a better way to do this
	rec.Header().Del("Etag")

	return rec.WriteResponse()
}

// executeTemplate executes the template contained in wb.buf and replaces it with the results.
func (t *Templates) executeTemplate(rr caddyhttp.ResponseRecorder, r *http.Request) error {
	var fs http.FileSystem
	if t.FileRoot != "" {
		repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
		fs = http.Dir(repl.ReplaceAll(t.FileRoot, "."))
	}

	ctx := &TemplateContext{
		Root:       fs,
		Req:        r,
		RespHeader: WrappedHeader{rr.Header()},
		config:     t,
	}

	err := ctx.executeTemplateInBuffer(r.URL.Path, rr.Buffer())
	if err != nil {
		// templates may return a custom HTTP error to be propagated to the client,
		// otherwise for any other error we assume the template is broken
		var handlerErr caddyhttp.HandlerError
		if errors.As(err, &handlerErr) {
			return handlerErr
		}
		return caddyhttp.Error(http.StatusInternalServerError, err)
	}

	return nil
}

// virtualResponseWriter is used in virtualized HTTP requests
// that templates may execute.
type virtualResponseWriter struct {
	status int
	header http.Header
	body   *bytes.Buffer
}

func (vrw *virtualResponseWriter) Header() http.Header {
	return vrw.header
}

func (vrw *virtualResponseWriter) WriteHeader(statusCode int) {
	vrw.status = statusCode
}

func (vrw *virtualResponseWriter) Write(data []byte) (int, error) {
	return vrw.body.Write(data)
}

var defaultMIMETypes = []string{
	"text/html",
	"text/plain",
	"text/markdown",
}

// Interface guards
var (
	_ caddy.Provisioner           = (*Templates)(nil)
	_ caddy.Validator             = (*Templates)(nil)
	_ caddyhttp.MiddlewareHandler = (*Templates)(nil)
)